Research On Error Characteristic Of The Three-phase Combined Tranformer By Using The Three-phase Calibration Method

With the continuous expansion of the scale of the electricity and the electrical distribution network constantly upgrading, the accuracy of the metering devices online have become increasingly demanding, energy metering devices’ accuracy not only relate to economic interests of all parties, but also an important indicator of many electric devices. The three-phase combined transformer has been a important electrical equipment in 10 k V, 35 k V electrical distribution network, its performance will directly affect the accuracy of monitoring, measurement in power system, and affect the reliability of relay protection operation. The relevant verification regulation for this type of transformer has not been worked out, the single-phase calibration method has been used to test three-phase combined transformer all the way, and its accuracy has been controversial. The three-phase three-element transformer’s error characteristics is analyzed is this paper by using three-phase calibration method.Firstly, discusses the basic operating principle of electromagnetic current transformer, introduces several current error detection methods for three-phase combined transformer, analyzes the influences of leakage currents under high voltage on internal current transformers, measures the errors by using different detection methods under high voaltage, and find that the error tested by using three-phase calibration method can reflect the true error precisely, the single-phase calibration method can not measure the error made by the leakage current under high voltage, the measurement method B is difficult to achieve.Secondly, the reason why valtage harmonic is produced in the three-phase three-element transformer is analyzed, expoud that hysteresis effect and the wiring are the main causes that the third harmonic appears in secondary voltage, and analyze the secondary side’s load’s influence on the content of harmonic, and it is verified by lots of experiments. In addition, a large number of experimental datas show that the valtage harmonic can influence the accuracy of the smart electrical energy meter, and the experiment shows that the error tested by single-phase calibration method is considered as qualified, and that is the reason to allow the three-phase combined transformer to operate inelectrical network.Describes the working principle of electromagnetic voltage transformer and the main factors that affect the error, tests the voltage error of the three-phase three-limb core transformer by using the single-phase calibration method and the three-phase calibration method, and the error datas show that the testing error datas have a big difference, and then the conclusion is made that three-phase magnetic circuit is unbalanced when the three-phase three-limb core transformer tested by using the single-phase calibration method, and suggests that the three-phase three-limb core transformer should be tested by using the three-phase calibration method.